I think "coastal leftism" is dead in the water if they want to win again in 2020.
Democrats need to go after blue collar whites in the north. Stronger unions, workers rights, things like that. Free trade will absolutely have to be reevaluated. They can't keep focusing on minorities and highly educated whites.
I think the Dems take 2020 easily but they took the rust belt votes for granted, and it really hurt them in this election.